Fluorosilicone lubricants containing tris (pentafluorophenyl) phosphine

ABSTRACT

SMALL AMOUNTS OF TRIS(PENTAFLUOROPHENYL) PHOSPHINE ARE ADDED TO FLUOROALKYLPOLYSILOXANE LUBRICANTS AS ANTIOXIDANTS AND ANTI-WEAR ADDITIVES.

United States Patent U.S. Cl. 25249.9 2 Claims ABSTRACT OF THE DISCLOSURE Small amounts of tris(pentafluorophenyl)phosphine are added to fluoroalkylpolysiloxane lubricants as antioxidants and anti-wear additives.

This invention relates to improved fiuoroalkylpolysiloxane lubricants which contain a minor amount of tris(pentafluorophenyl)phosphine. Addition of the phosphine inhibits oxidation of the fluids and enhances the anti-wear characteristics of metal on metal lubrication.

'Organophosphorus compounds are known lubricity additives for organopolysiloxanes in general-see U.S. Pat. 2,684,336. The use of phosphates and phosphites as antiwear additives in fluorosilicone lubricants is discussed in US. Pat. 3,386,917.

By the practice of the present invention, wherein tris- (pentafluorophenyl)phosphine is used as an additive, not only are the anti-wear characteristics of fluorosilicone lubricants improved, but the oxidative stability of the fluid is increased, thus preventing the formation of sludge at higher temperatures.

Accordingly, it is an object of the invention to provide an improved fluoroalkylpolysiloxane lubricant.

The invention provides a composition consisting essentially of (1) 100 parts by weight of an organopolysiloxane fluid containing at least 70 mol percent of units, any remaining units being of the formula (RSiO (R' SiO) or (R' SiO in which R, is a perfluoroalkyl radical of no more than 12 carbon atoms, R is a lower alkyl radical of no more than 6 carbon atoms or a phenyl radical; R is a monovalent hydrocarbon or monovalent halohydrocarbon radical; and

(2) from 0.1 to 8 parts by weight of tris(pentafluorophenyl)phosphine.

As described above R; can be any perfluoroalkyl radical of no more than 12 carbon atoms, for example, heptafluoropropyl, perfluorobutyl, perfluoroisohexyl, prefluorooctyl, perfiuorododecyl or, preferably, trifluoromethyl.

R can be the phenyl radical or any of the lower alkyl radicals such as methyl, isopropyl, t-butyl or hexyl. The same or different R substituent can be bonded to the same silicon atom.

R can be any monovalent hydrocarbon radical, for example, alkyl radicals such as methyl, ethyl, isopropyl, 2-ethylhexyl or octadecyl; aliphatically unsaturated radicals such as vinyl, allyl, ethynyl, butadienyl or 4-hexenyl; or aryl-containing radicals such as phenyl, tolyl, Xenyl, naphthyl, benzyl, or 2-phenylpropyl.

R can also be any monovalent halohydrocarbon radical, for example, 3,3,3-trifluoropropyl, chloropropyl, bromohexyl, chloroallyl, dibromophenyl, chlorophenyl, a,a,u-trifluorotoyl or chloroxenyl.

3,629,115 Patented Dec. 21, 1971 "ice The tris(pentafiuorophenyl)phosphine additive is a known compound and can be prepared by the reaction of pentafluorophenyl magnesium bromide and phosphorus trrchloride. Only minor amounts, from 0.1 to 8 parts per 100 parts of lubricant, are necessary to obtain the desired oxidative stability. Greater amounts can be used if desired but are generally uneconomical. Depending upon the specific composition of the fluid, insolubility of the phosphine at greater concentrations may present problems.

The following examples are illustrative of the invention which is properly dilineated in the claims.

EXAMPLE 1 To determine the efficiency of tris (pentafluorophenyl) phosphine as an anti-oxidant, various amounts of the compound were mixed with portions of trimethylsiloxyendblocked 3,3,3-trifluoropropylmethylpolysiloxane fluid having a viscosity of 300 cs. at F, The oxidative stability of these additive-containing fluids was tested by observing the time required for the fluids to gel at certain high temperatures in open containers. Test conditions and results are given below:

A mixture of 50 grams of the above described fluorosilicone fluide (contain 1 weight percent tris(pentafluorophenyl)phosphine) and 0.5 gram of mineral oil was placed in a 250 milliliter beaker and heated for 2 hours at 550 F. After heating for this period of time, there was no formation of sludge or gummy deposits. This is to be contrasted with testing when an additive-free mixture of the same components is utilized, wherein there is formation of a large amount of sludge. This ability to prevent sludge formation is especially important in those fluids used in hydraulic systems which are highly susceptible to plugging.

EXAMPLE 2 Weight percent additive in fluid: Scar dia. (mm.)

None .90 1% .47 5% .40

The additive-containing fluid also gave improved lubrication at high loadings in the four-ball test. With test conditions of 1200 r.p.m. at 167 F. for 30 minutes at a loading of 10 kilograms of steel on aluminum, the addition of 1% tris(pentafluorophenyl)phosphine to the lubricant reduced the scar diameter from 4.9 millimeters to 0.49 millimeter.

4 EXAMPLE 3 R is a monovalent hydrocarbon or monovalent halohydrocarbon radical; and (2) from 0.1 to 8 parts by weight of tris(pentafiuoropheny1)phosphine.

When from 1 to 7 grams of tris(pentafiuoropheny1) phosphine are added to 100 grams of QH, QH; QHzCH 5 2. The composition of claim 1 wherein ingredient (caHachsiom) 1 S 1 3 OII'SICHE (l) is a polymer of 3,3,S-trifluoropropylmethyl siloxane CH, CH, (3H7 8% units which have trimethylsiloxy endblocking units. CHgCiFn 10 CHICFQ 10 3 07F, 3 the oxidative stability of the lubricant is improved. References Clted That which is claimed is: 10 UNITED STATES PATENTS 1. A composition consisting essentially of 3,078,229 2/1963 Cox X (l) 100 parts by weight of an organopolysiloxane fluid 3,115,465 12/1963 orloff et aL X containing at least 70 mol percent Of 3 3 5 790 5 19 Davies et 1 252 52 3,386,917 6/1968 Schiefer 25249.9 15 3,393,151 7/1968 Dolle et a1. 252-499 R 3,481,872 12/1969 Dolle et a1. 252-493 units, any remaining units being of the formula s o l s o s o in hi DANIEL E. WYMAN, Primary Examlner R, is a perfiuoroalkyl radical of no more than 12 20 w CANNON, Assistant Examiner carbon atoms,

R is a lower alkyl radical of no more than 6 US. Cl. X.R.

carbon atoms or a phenyl radical; 25254 

